Apparatus for quantitative indicating of small and rapid volume changes in a part of an extremity

ABSTRACT

In an apparatus for quantitative indicating of small and rapid volume changes in a part of an extremity there is provided a plethysmograph with a rigid shell and a number of pivoted rigid plates at each end of the shell partially overlapping each other. These plates at each end of the shell are enclosed in an evacuable casing and are adjustable to be sealingly engaged with the extremity together with said casing, said plates being locked in their adjusted position by the evacuation of said casing.

United States Patent [54] APPARATUS FOR QUANTITATIVE INDICATING OF SMALL AND RAPID VOLUME CHANGES IN A PART OF AN EXTREMITY 4 Claims, 4 Drawing Figs. [52] US. Cl 128/2.05 [51] Int. Cl. A61b 5/02 [50] Field of Search 128/2.05, 2,

2.1; 128/87, 132 (Cursory), 133, 298, 299, 30.2, 24 (Inflatable Splint Digest); 3/20 Primary Examiner-Richard A. Gaudet Assistant Examiner-Kyle L. Howell Attorney-Beale and Jones ABSTRACT: In an apparatus for quantitative indicating of small and rapid volume changes in a part of an extremity there is provided a plethysmograph with a rigid shell and a number 'of pivoted rigid plates at each end of the shell partially overlapping each other. These plates at each end of the shell are [56] References Cited enclosed in an evacuable casing and are adjustable to be UNITED STATES PATENTS sealingly engaged with the extremity together with said casing, 1,775,442 9/1930 Sarason 128/402 said plates being locked in their adjusted position y the 170,217 11/1875 Allen 128/24 evacuation ofsaid casing INTEG RATOR 15 VOLUME TO ECG-RECORDER AMPLIFIER FLOW TRANSDUCER 12 Kalil/111111 ZIIIIIIIll/l/JN /5 I l I I l 1 l I l l l I s ,1' I i l -2 x I t r 1 I l l l l 1 I iiinii; n u

Patented March 16, 1971 3,570,474

INTEG RATOR 15 VOLUME TO ECG-RECORDER Fig.1 AMPLIFIERII,

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10 ml/s 10 ml/s APPARATUS FOR QUANTITATIVE INDICATING OF SMALL AND RAPID VOLUME CHANGES IN A PART OF AN EXTREMITY The present invention relates to an apparatus for quantitative indicating such as measuring and/or recording of small and rapid volume changes in a part of an extremity, known as plethysmograph, and more particularly to means for obtaining a sealing contact between a rigid shell forming the main body of such plethysmograph, and the extremity when using the plethysmograph, while rigidly maintaining said plethysmograph in the position on the extremity.

In prior art plethysmographs this rigid contact with the extremity was achieved by means of diaphragms provided at each end of the rigid plethysmograph tube. Such diaphragms consisted of rigid laminae, each of which was displaceable at right angles to the extremity and adapted to be fixed with part of the laminae applied to the extremity. However, such diaphragms will never seal completely between adjacent laminae or against the extremity. It has therefore become necessary to insert a sealing means, e.g. formed as a rubber sleeve, between the diaphragm laminae and the extremity, which must be in contact with the inside of the laminae as well as the extremity so that the fluid enclosed by the plethysmograph, i.e. air or liquid, will be enclosed between said sleeve and the rigid shell of the plethysmograph. The mounting of the sleeve on the laminae and the extremity provides difficulties as a result of air pockets forming in spaces between the laminae, whereby the rigidity of the apparatus is reduced and consequently also the accuracy of the indicated results. Further, the mounting of prior art diaphragms is time consuming.

In order to avoid the drawbacks associated with prior art apparatus of the kind herein described, there is provided according to the invention an apparatus for quantitative indicating of small and rapid volume changes in a part of an extremity comprising a plethysmograph having a rigid tubular shell to be disposed on theextremity surrounding said part thereof, the volume changes of which are to be indicated, sealing means at each end of said shell to seal the shell against the extremity, said sealing means comprising a diaphragm consisting of a number of rigid plates arranged circumferentially of said shell in partially overlapping relationship and adjustably connected therewith to be engaged with the extremity and a flexible covering enclosing said plates, which is connected to said shell, and means for connecting the interior of said covering to air evacuating means, said plates being fixedly retained in their adjusted position when the interior of said covering is evacuated, and means for connecting said plethysmograph to indicating means.

An apparatus constructed as proposed according to the invention can be easily and quickly mounted and fixed on the extremity because the plates of such means are hingedly or displaceably adjustable into contact with the extremity. After evacuating the covering enclosing the plates, these are fixed or locked in the adjusted position by the outer air pressure, which presses the plates against each other, whereby a rigid and sealing contact against the extremity is obtained.

The invention will be described in more detail with reference to the accompanying drawing, in which:

FIG. 1 is a sectional view of a plethysmograph having diaphragm means according to the invention, and applied to an extremity;

FIG. 2 is a view as that in FIG. 1 and illustrates a modification of the plethysmograph; and

FIGS. 3 and 4 are diagrams illustrating the measured results obtained by means of the plethysmograph.

FIG. 1 shows a plethysmograph apparatus 1 mounted on a section 2 of an extremity 3. The apparatus comprises a rigid tube 4, in the two ends of which diaphragm means 5 are mounted. These form the end walls of the apparatus and serve as rigid sealing means sealingly engaging extremity 3. Diaphragm means 5 each consist of several rigid plates 6 partly overlapping each other and mounted around the periphery of the tube ends to be adjustable against and from extremity 3. Plates 6 may be pivoted to tube 4 by hinges formed by a flexible material such as rubber or plastic and providing a flexible connecting web between the plates and the tube. Each of the plates occupies a small portion of the tube periphery. Since the plates are adjustable the diaphragm means can be mounted at any portion of an extremity 'by changing the conicity of such means.

Plates 6 at each end of tube 4 are completely enclosed in soft and flexible coverings 7 which are connected in an airtight manner with the adjacent tube ends. A hose 8 or the like communicates with the interior of the coverings while its other end can be connected to an air suction device (not shown) for evacuating the airspace within the coverings. Such evacuation of the coverings entails that the plates 6 are pressed against each other in the position adjusted to the extremity under sealing contact therewith, covering 7 contributing to this result being achieved.

This arrangement not only provides complete sealing between the various laminae and between the laminae and the extremity but also provides an excellent rigidity in the whole arrangement, which is important in order to obtain accurate measuring results. As a matter of fact it should be noted that the volume changes to be indicated are very small, e.g. in the range of 0.1 to 1 ml.

Tube 4 has a connection 9 opening to the atmosphere, by which the apparatus is connected to an indicating apparatus. As shown in FIG. 1 there is provided in connection 9 a flowmeter 11 which is sensitive to airflow out of or into the plethysmograph tube 4 through connection 9, caused by volume changes of section 2 of extremity 3 enclosed by tube 4. Flowmeter 11 may be a pneumotachograph which offers extremely small resistance to the airflow, and differential pressure across such pneumotachograph is sensed by a pressure transducer 12 communicating with connection 9 through tubes 13 on opposite sides of the pneumotachograph. This pressure represents flow through the pneumotachograph and is converted into an electric signal by transducer 12. This signal is applied to an amplifier 14 which applies the amplified electric signal to an integrator 15 wherein the flow signal is in tegrated with respect to time in order to provide a /volume registration. A flow signal provided by amplifier l4 and a volume signal provided by integrator '15 are applied to an ECG recorder to linearly record volume changes of section 2. The flow signal is calibrated with a known constantflow and the volume signal is calibrated with known volumes from a syringe.

FIGS. 3 and 4 show the measuring precision obtained by means of the apparatus according to the invention. The differential pressure emanating from the apparatus is measured and amplified and then recorded by the ECG. recorder. FIG. 3 shows the recording of the thigh of a healthy man-The volume in the apparatus was 1 l. and the pulse volume changes amounted to 0.7 ml. The recording was typical of a thigh'at rest. FIG. 4 is a recording of the blood flow under venous occlusion.

FIG. 2 shows a modification of the plethysmograph according to FIG. 1. In this embodiment a hose 10 extends through tube 4. Hose 10 is secured to the ends of coverings 7 at the peripheral parts thereof facing the extremity, e.g. by welding, in order to obtain good sealing against coverings 7. Hose 10 is a resilient so that it can follow the movements of coverings 7. This arrangement makes it possible to use a liquid as measuring medium, such liquid being enclosed in the annular chamber formed inside tube 4 by the inner surface of the tube and hose 10.

The invention is not, of course, limited to the embodiments shown, but modifications may be made within the scope of the claims. Thus, the plates may be displaceably mounted, e.g. have a slot or groove in the central portion, with which a pin attached to the tube will engage. An arrangement of this king permits angular displacement of the plates against the extremity.

I claim:

'1. Apparatus for quantitative indicating of small and rapid volume changes in a part of an extremity comprising a plethysmograph having a rigid tubular shell adapted to be disposed about the extremity surrounding said part thereof, the volume changes of which are to be indicated, sealing means at each end of said shell adapted to seal the shell against the extremity, said sealing means comprising a diaphragm consisting of a number of rigid plates arranged circumferentially of said shell in partially overlapping relationship and adjustably connected therewith, said plates being adapted to be engaged with the extremity and a flexible covering enclosing said plates which covering is connected to said shell, and means for connecting the interior of said covering to air-evacuating means, said plates being fixedly retained in their adjusted position when the interior of said covering is evacuated, and means for connecting the interior of said shell to indicating means; and indicating means responsive to volume changes within said tubular shell of said plethysmograph.

2. Apparatus as claimed in claim 1 in which said covering forms an annular sleeve adapted to be disposed around the extremity.

3. Apparatus as claimed in claim 1 in which an elastic wall is provided in said shell extending between said coverings in opposite ends of the shell to define together with said shell a fluidtight annular chamber inside the shell, said means for connecting said plethysmograph to said indicating means communicating with said chamber.

4. Apparatus as claimed in claim 1 in which said indicating means includes transducer means for sensing said volume changes and converting said volume changes to corresponding electric signals, and means for displaying said electric signals. 

1. Apparatus for quantitative indicating of small and rapid volume changes in a part of an extremity comprising a plethysmograph having a rigid tubular shell adapted to be disposed about the extremity surrounding said part thereof, the volume changes of which are to be indicated, sealing means at each end of said shell adapted to seal the shell against the extremity, said sealing means comprising a diaphragm consisting of a number of rigid plates arranged circumferentially of said shell in partially overlapping relationship and adjustably connected therewith, said plates being adapted to be engaged with the extremity and a flexible covering enclosing said plates which covering is connected to said shell, and means for connecting the interior of said covering to air-evacuating means, said plates being fixedly retained in their adjusted position when the interior of said covering is evacuated, and means for connecting the interior of said shell to indicating means; and indicating means responsive to volume changes within said tubular shell of said plethysmograph.
 2. Apparatus as claimed in claim 1 in which said covering forms an annular sleeve adapted to be disposed around the extremity.
 3. Apparatus as claimed in claim 1 in which an elastic wall is provided in said shell extending between said coverings in opposite ends of the shell to define together with said shell a fluidtight annular chamber inside the shell, said means for connecting said plethysmograph to said indicating means communicating with said chamber.
 4. Apparatus as claimed in claim 1 in which said indicating means includes transducer means for sensing said volume changes and converting said volume changes to corresponding electric signals, and means for displaying said electric signals. 